High frequency radio relay system



Sept. 1941- H. E. GOLDSTINE 2,257,094

HIGH FREQUENCY RADIO RELAY SYSTEM Filed Aug. 1, 1939 2 Sheets-Sheet l I OUTGO/NG .S IGNAL INCOM/NG SIGNAL R; E AMPLIFIER IDENTIFYING KE YER INVENTOR. v HALLA N E. GOLDSTINE ATTORNEY.

Sept. 30, 1941. H. E.GOLDST!NE HIGH FREQUENCY RADIO RELAY SYSTEM Filed Aug. 1, 1939 2 Sheets-Sheet 2 IN OUT R. F. AMPLIFIER AUDIO INV EN TOR. HALLA N E. GOLDS T INE ATTORNEY.

Patented Sept. 30, 1941 HIGH FREQUENCY RADIO RELAY SYSTEM 7 Hallan E. Goldstine, Rocky Point, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application August 1, 1939, Serial N 0. 287,700

12 Claims.

The present, invention relates to ultra short wave relay systems and, more particularly, to monitoring means for relay stations of the aforesaid systems.

In point to point communications using ultra high frequencies it is often desirable to use one or more relay stations between the source of origin of the signals and the final destination. This is not only for the purpose of maintaining the signal above a predetermined level but, also, is necessary due to the fact that the curvature of the earth prevents direct communication at these high frequencies beyond the visual horizon. These relay stations ordinarily receive signals on a directional antenna, amplify the signals without frequency conversion and retransmit the amplified signals in the desired direction from a directive antenna. Thus, the equipment between the receiving and transmitting antenna of a relay station often involves only a radio frequency amplifier which may be left in continuous operation. The relay station may be left unattended for comparatively long periods of time. In order to reliably maintain a continuous channel between the first transmitter and the final receiver it is desirable to monitor the operation of each relay station from either the transmitter or the receiver or from some other convenient point instead of relying upon personal supervision at each station.

An object, therefore, of the present invention is a provision of means for. continuously monitoring each relay station in a system, as aforesaid.

Another object of the present invention is to provide a continuous indication as to the operation of each of the relay stations in a system, as aforesaid.

Still another object is to provide means for giving an alarm in case of failure of any part of each of said stations.

Still another object is to provide means for giving an alarm in case the amplifier of any one of the relay stations ceases to function.

Still a further object of the present invention is to provide means for giving positive indication in case of breakdown as to which relay station has failed. to operate.

My invention contemplates the provision of one or more monitoring channels connecting each of the relay stations to a given monitoring point. At each of the relay stations I provide an audio frequency oscillator, the feedback link of which is constituted by the amplifying channel of the radio frequency amplifier at the station. As long as the radio frequency amplifier and oscillator at each station are functioning correctly an audio tone is fed from the station into one of said monitoring channels, thus giving a positive indication of the operativeness of the amplifier at each station. When radio frequency energy appears in the output of the radio frequency amplifier due to the transmission of signals along the network, a portion of the sig- .10 nal is rectified and the resultant direct current is used to bias the audio frequency oscillator to inoperativeness, thus causing a cessation of indication at the monitoring location. Thus, the monitoring operator, knowing a signal is being transmitted, and if it is not being received at the receiver, may determine by an inspection of the indications at the monitoringlocation at which relay station the trouble exists. By using a different and distinct monitoringtone for each station and frequency selective indicators at the monitoring location a single telephone line may be used for the entire system.

As a modification, the relay station may also include a second oscillator to give a different tone if the radio frequency amplifier is working and no signal is being transmitted thus more positively isolating the trouble in case trouble exists. Furthermore, separate audio tone sources may be provided to be applied to the monitor line .30 for various other indications, such as failure of power supply or to indicate if the power supply has been changed from the public service mains to emergency power.

Other objects and features of the present in- 5 vention may be understood from the following detailed description, which is accompanied by drawings in which Figure 1 shows schematically one form of the present invention and Figure 2 shows a modification thereof.

Referring, now, to Figure 1, reference numeral i indicates a receiving antenna within a directive reflector R, while 2 indicates a transmitting an.- tenna within a similar directive reflector. The signal picked up by receiving antenna I is applied to radio frequency amplifier 3 through the appearing in output coil 5 is applied through a transmission line to the transmitting antenna 2 and thus transmitting to the next succeeding recoupling coil 4. The resultant amplified signal transformer ID. The output circuit I I of tube 9 is connected to the neutral point of input coil I through a coupling condenser I2. It will be seen in the output circuit of the radio frequency amplifier a portion of the signals are rectified by ship, thus assuring a complete lack of interaction between the two functions of the radio frequency amplifier. The neutral points of coils 4 and 5 are effectively at ground potential only as far as radio'frequency energy isconsidered. Sufficient low frequency coupling exists in the radio frequency amplifier 3 to permit it to operate as a push-push feedback link for the audio frequency oscillator. Sustained oscillations which are therefore built up in the audio amplifier may be ap plied 'by mean's of winding I3 of transformer It to {a monitor channel by means of'jack I4. The monitoring channel may be a telephone line connecting all of the relay stations to a common monitoring location or a separate radio channel may be provided. In the latter case, the output from jack I I will be used to modulate a radio transmitter in the conventional manner.

' A constant audio tone will appear in the monitoring channel as long as radio frequency amplifier 3 is-in an operative condition. Upon the arrival of signals at receiving antenna I these signals are amplified in radio frequency amplifier 3 and a portion of the amplified signals is applied to rectifier I5 thus causing a direct voltage to be built up across resistor Hi. This voltage is applied to the input circuit -'I of tube 6 thus biasing the tube to cutoff and stopping the audio frequency tone I which is applied to the monitoring channel. Thus a positive indication is given that the signal is being received, amplified, and applied to the outgoing transmitting antenna. If desired, an identifying keying device '24 maybe insertedin the circuit between the monitoring channel and winding I3 of transformer ID in order to give a code identification of the relay station so that the-station sendin'g'out the signal may be clearly identified.

If the audio oscillators at 'each of the relay stations are each tuned to a distinct audio fre- "quency a singlemonitoring-channel may be employed-and the tones separated by means of filters at the central monitoring station. In this case,

or course, the identifying keyer 24 will notjbe I necessary. i

a The modification of the invention shown in Figure 2 is'si'milar tothat shown in-Figure 1', with theexception of the addition of an audio oscillarim 2'! which is tuned to a diiferent frequency thanthe oscillator employing tubes 6 and '9 and" described-with reference to "Figure 1. The output 'of'a-udio oscillator 2'I is applied to the grid f vacuum tube 28 which is normally biased to cutrectifier 25 and cause a direct voltage to appear across resistor 26. This direct voltage overcomes the bias on the grid of tube 28 due to the potential source 29 and allows the tone generated by audio oscillator 21 to appear in the monitoring channel. In this modification a tone of one frequency,

say, 1000 cycles, mayibe generated by the audio oscillator embodying tubes 6 and 9 and appears in the monitoring channel when the radio frequency amplifier is in an operative condition. The presence of signals in the output of the radio frequency amplifier causes this tone to be cut off applied to the monitoring channel} Whill have particularly shown and described several modifications of my invention, it to be clearly understood. that my invention is not limited thereto but that modifications within the scope of the invention may be made.

I claim:

1. In a radio relay station, a radio frequency amplifier having an input and an output, an audio frequency oscillator, means for utilizing said radio frequency amplifier as a feedback link for said oscillator whereby said oscillator operates whenever said amplifier is operative, and means connected to the output of said radio frequency amplifier for disabling said oscillator in the presence of radio frequency signals in the output of said'ampli'fier. 7

2. In a radio relay station, a radio frequency amplifier having an'input and an output, means responsive to an operative condition of said amplifier for applying an identifying signal to a monitoring channel, means responsive to presoperates whenever said amplifier is operative and means connected to the outputof said radio frequency amplifier for biasing said oscillatorinoperativeinthe presence-of signals'in the output of 'saidamp'lifier.

- 4. In a radio relay station, a radio. frequency amplifier having an input, and an output, .an audio frequency oscillator, means for utilizing said radio frequency'amplifier as a feedback link for said oscillator whereby said oscillator operates wheneversaid amplifier is operativeand off by a source'of potential 29. The output circuit vof tube 28 is completed through coupling transformer '3 3'to output jack 34. Through the "output-jackffl the tone generated by audio oscillator '21 may be applied to the same monitoring channelfasused for the tone carried by output jack I4;

In order to'control the'presence or absence of 'the'tone in themonitoring channel due to audio oscillator 2'I,"I have provided a second rectifier 2 5 -al socoupled,to the output circuit of the radio frequency amplifier-3. I-nthepresence of signals means connected to the output of said radio frequency amplifier for biasing said oscillator inoperative in the presence of signals in the output of said amplifier, a second oscillator, output circuits for each of said oscillators, means for normally preventing application of oscillations from said second oscillator to its output circuit and means connected to. the output 'of said radio frequency amplifier for'causing said inoperative oscillator to become operative in the presence of signals in said "amplifier output.

5. In a radio relay station,la radio frequency amplifier having an input and an'output, an

audio frequency amplifier having an input connected to the output of said radio frequency amplifier and an output connected to the input of said radio frequency amplifier whereby said audio frequency amplifier oscillates whenever said radio frequency amplifier is operative, and means connected to the output of said radio frequency amplifier for biasing said audio frequency amplifier inoperative in the presence of signals in said radio frequency amplifier output circuit.

6. In a radio relay station, a radio frequency amplifier having an input and an output, an audio frequency amplifier having an input connected to the output of said radio frequency amplifier and an output connected to the input of said radio frequency amplifier whereby said audio frequency amplifier oscillates whenever said radio frequency amplifier is operative, means for connecting said audio frequency amplifier to a monitoring channel and means connected to the output of said radio frequency amplifier for biasing said audio frequency amplifier inoperative in the presence of signals in said radio frequency amplifier output circuit, an audio frequency oscillator, and means for connecting said oscillator to a monitoring channel, means for maintaining said last mentioned means normally inoperative and means connected to the output of said radio frequency amplifier and responsive to the presence of signals therein for causing said inoperative means to become operative.

7. In a radio relay station, a radio frequency amplifier having an input and an output, an audio frequency amplifier having an input connected to the output of said radio frequency amplifier and an output connected to the input of said radio frequency amplifier whereby said audio frequency amplifier oscillates whenever said radio frequency amplifier is operative, means for connecting said audio frequency amplifier to a monitoring channel and means connected to the output of said radio frequency amplifier for biasing said audio frequency amplifier inoperative in the presence of signals in said radio frequency amplifier output circuit, an audio frequency oscillator, and means for connecting said oscillator to said monitoring channel, means for maintaining said last mentioned means normally inoperative and means connected to the output of said radio frequency amplifier and responsive to the presence of signals therein for causing said inoperative means to become operative.

8. In a radio relay station, a radio frequency amplifier having an input and an output, an audio frequency oscillator, means for utilizing said radio frequency amplifier as a feedback link for said oscillator whereby said oscillator operates whenever said amplifier is operative, a rectifier having its input connected to the output of said radio frequency amplifier, means connecting said rectifier to said oscillator for biasing said oscillator inoperative in the presence of signals in said amplifier and means for coupling said oscillator to a monitoring circuit.

9. In a radio relay station, a radio frequency amplifier having an input and an output, an audio frequency oscillator, means for utilizing said radio frequency amplifier as a feedback link for said oscillator whereby said oscillator operates whenever said amplifier is operative, a monso that said means is rendered operative in the presence of signals in said radio frequency amplifier output.

10. In a radio relay station, a radio frequency amplifier having an input and an output, an audio frequency oscillator, means for utilizing said radio frequency amplifier as a feedback link for said oscillator whereby said oscillator operates whenever said amplifier is operative, a monitoring circuit connected to said oscillator, a second oscillator, an amplifier coupling said second oscillator to said monitoring circuit, means for biasing said amplifier to cut-off, a pair of rectifiers connected to the output of said radio frequency amplifier, load resistances for each of said rectifiers, means for connecting the load resistance of one of said rectifiers to said first oscillator so that said oscillator is rendered inoperative in the presenceof signals in said radio frequency amplifier output and means for connecting the other of said load resistances to said coupling amplifier so that said amplifier is rendered operative in the presence of signals in said radio frequency amplifier output.

11. In a radio relay station, a radio frequency amplifier having an input and an output, an audio frequency amplifier having an input connected to the output of said radio frequency amplifier and an output connected to the input of said radio frequency amplifier whereby said audio frequency amplifier oscillates whenever said radio frequency amplifier is operative, means connected to the output of said radio frequency amplifier for causing said audio frequency amplifier to become inoperative in the presence of signals in said radio frequency am plifier output circuit and means for coupling said audio frequency amplifier to a monitoring circuit.

12. In a radio relay station, a radio frequency amplifier having an input and an output, an audio frequency amplifier having an input connected to the output of said radio frequency amplifier and an output connected to the input of said radio frequency amplifier whereby said audio frequency amplifier oscillates whenever said radio frequency amplifier is operative, and means connected to the output of said radio frequency amplifier for causing said audio frequency amplifier to become inoperative in the presence of signals in said radio frequency amplifier output circuit, an audio frequency oscillator, and means for connecting said oscillator and said audio frequency amplifier to a monitoring channel, means for maintaining said last mentioned means normally inoperative and means connected to the output of said radio frequency amplifier and responsive to the presence of signals therein for causing said inoperative means to become operative.

I-IALLAN E. GOLDS'I'INE. 

